We request support for the third annual single chromosome workshop on human chromosome 9. The purpose of these meetings are to: 1) provide a forum for all major groups mapping chromosome 9 to identify and exchange mapping information; probes (including genes, STSs, cosmids, YACs, P1 clones); somatic cell hybrid lines; chromosome 9-specific libraries; mapping strategies and approaches both in use and planned; database resources and management tools (programs); 2) create a consensus genetic and physical map of the chromosome; 3) stimulate contact and exchange between human chromosome 9 mappers and those mapping syntenic regions of the mouse and other genomes. The first and second international chromosome 9 workshops were attended by about 70 participants from nine countries, and served to bring together all major elements of the chromosome 9 mapping community, providing significant coordination for future mapping efforts. The report of the second meeting is in press. We plan a similar scientific agenda at subsequent meetings, with subgroups to work on several different issues: a map of chromosome 9p, a map of 9qcen - q33, a map of 9q33 - qter, global mapping strategies and integration of different types of maps, construction of a CEPH consortium map, chromosome 9 resources, mapping of the ten known, but unidentified disease genes on 9, and comparative mapping in human and mouse with special reference to human chromosome 9.